Management of cell-specific address information

ABSTRACT

A method in a communication network comprising a core network and a radio access network. At least one target cell is defined for at least one originating cell controlled by a first radio access network node. A request for a packet switched communication address of a second RAN node of the target cell is delivered to the second RAN node, and a response comprising the requested address is returned. The request and the response are transferred between the first radio access network node and the second radio access network node in information containers that are transparent to the core network. The received address information is stored in the first radio access network node for facilitating delivery of data packets between the originating cell and the target cell. Based on the stored cell-specific information, information may be exchanged between the nodes controlling the cells without congesting the essential core network elements and interfaces.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Divisional of U.S. patent application Ser. No. 10/924,199,filed Aug. 24, 2004. The disclosure of the prior application is herebyincorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The invention relates to telecommunications and more particularly to amethod of managing cell-specific address information in a communicationnetwork, and to an apparatus implementing the invented method.

BACKGROUND OF THE INVENTION

The packet domain of modern communication systems uses packet-modetechniques to transfer user data and signaling in an efficient manner.Strict separation between the radio subsystem and network subsystem istypically maintained, which allows the network subsystem to be shared byseveral radio access technologies.

The air interface of the radio system, on the other hand, allows signalsfrom many users to be multiplexed over the same physical resource.Resources are given to a user upon need and are reallocated immediatelythereafter. In order to accomplish this, the radio access networkcomprises functional elements for controlling the use of the airinterface. In order to be able to appropriately control the radioresources, these functional elements need diverse cell-specificinformation on cell-specific groups of other cells. For circuit switchedfunctions the specifications define exhaustively data transfer andinformation exchange procedures, which ensure that valid and relevantinformation is provided timely for the functional control elements.However, in the packet domain, some problematic deficiencies have beenidentified.

For example, a Network Assisted Cell Change (NACC) function reduces theservice outage time at cell reselection. NACC allows support to be givento the mobile stations as system information for the target cell beforethe mobile station performs the cell reselection. In order to be able toprovide NACC, a functional unit handling the handover of a mobilestation from a source cell to a target cell needs a certain set ofsystem information messages of the target cell. 3GPP specifies a RANInformation Management (RIM) procedure that allows delivery ofinformation between Radio Access Network (RAN) nodes transparently tothe core network. However, RIM procedures are routed via the corenetwork, and incurring of additional load and thus increasing the riskof congestion of the interface between the radio system and the networksystem should be carefully avoided.

As another example, the 3^(rd) Generation Partnership Program (3GPP)standards further define network controlled cell reselection (NCCR)procedure, wherein a cell reselection is initiated for an individualmobile station by the network. In general, cell-specific load reportsare delivered in specific types of circuit switched handover messages.Based on this information, load information would be available for thepurpose of load-based cell reselection only in cases where the mobilestation has had circuit switched connection with handovers betweencells. Such dependency of packet domain operations on the circuitswitched operations is not acceptable. Some advanced base stationcontrollers allow checking of target cell loads and resourceavailabilities before a controlled cell change order is given. This is,however, possible only when the source and the target cells arecontrolled by the same base station controller. The information isequally needed in other configurations, as well.

BRIEF DESCRIPTION OF THE INVENTION

An object of the present invention is thus to provide a method and anapparatus for implementing the method so as to solve the above problemsin operations of the packet domain. The objects of the invention areachieved by a method and an arrangement which are characterized by whatis stated in the independent claims. The preferred embodiments of theinvention are disclosed in the dependent claims.

The invention is based on the idea of facilitating exchange ofcell-specific information as much as possible by means of direct packetswitched communication between the radio access network nodes thatcontrol the relevant cells. This is accomplished by storing addressinformation on at least one other cell into a radio access node thatcontrols the use of the radio resources in one cell. Since the number ofcells in mobile communication systems is typically big, a procedure thatallows automatic management of the address information in the cell isestablished.

Based on the stored cell-specific information, any subsequentinformation may be exchanged directly between the nodes controlling thecells without congesting the essential core network elements andinterfaces. Some further advantages of the invention are described alongwith the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be described in greater detail bymeans of preferred embodiments with reference to the attached drawings,in which

FIG. 1 illustrates the functional architecture of a communicationsystem;

FIG. 2 illustrates alternative locations of a PCU;

FIG. 3 a illustrates a configuration of a group of neighboring cells;

FIG. 3 b illustrates the logical configuration of base station systemsincluding the cells of FIG. 3 a;

FIG. 4 a illustrates a configuration of two separate base stationsystems BSS1 and BSS2:

FIG. 4 b illustrates an embodiment of the present invention in theconfiguration of FIG. 4 a;

FIG. 5 illustrates an exemplary signaling sequence of neighbor cell PCUaddress query; and

FIG. 6 illustrates the logical configuration of a packet control unit.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is applicable to different telecommunicationssystems, e.g. in the GSM system together with the general packet radioservice (GPRS) or in new third-generation telecommunications systemssuch as the UMTS (Universal Mobile Telecommunications System) or theWCDMA. In the following, the preferred embodiments of the invention aredescribed by means of the GPRS/GSM radio system without limiting theinvention to this particular radio system.

The block chart of FIG. 1 illustrates the functional architecture of acommunication system that enables packet data transmission betweenmobile data terminals and external data networks. The first leg of thesystem illustrates a mode of operation of the mobile station (MS) 100connected to the Core Network (CN) 105 via General Packet Radio Service(GPRS) system, the GSM system (Global System for Mobile communications)acting as a Radio Access Network (RAN). Generally, the basic structureof a GSM network comprises two parts: a base station system (BSS) 110and a network subsystem (NSS). The GSM BSS communicates with mobilestations (MS) 100 via radio connections over a radio interface Um 115.In the base station system BSS 110 each cell is served by a basetransceiver station (BTS) 120. The base station 120 is connected to abase station controller (BSC) 125, which controls the radio frequenciesand channels used by the base station. The base station controller BSC125 is connected over an A-interface 130 to a mobile switching centre(MSC) 135, i.e. as a part of GSM NSS to the core network NC 105 of thesystem.

The Serving GPRS Support Node (SGSN) 140 keeps track of the location ofindividual mobile stations and performs security functions and accesscontrol. The SGSN 140 is connected to the GSM base station systemthrough the Gb interface 145. The Gateway GPRS Support Node (GGSN) 150provides interworking with packet data networks, and is connected withSGSNs via an IP-based packet domain PLMN backbone network.

In order to use GPRS services, an MS shall first make its presence knownto the network by performing a GPRS attach. This makes the MS availablefor SMS over GPRS, paging via the SGSN, and notification of incomingpacket data. In order to send and receive packet data by means of GPRSservices, the MS shall activate the Packet Data Protocol context that itwants to use. This operation makes the MS known in the correspondingGGSN, and interworking with data networks can commence.

A serving GPRS support node 140 (SGSN) is arranged to serve a mobilestation by sending or receiving packets via the BSS. Each support nodeSGSN manages the packet data service in the area of one or more cells ina cellular packet radio network. A mobile station 10, which is in acell, communicates with the BSS 110 over the radio interface Um 115 andfurther through the Gb interface 145 with the SGSN 140 to the servicearea of which the cell belongs. This mode of operation of the MS, whenconnected to the Core Network via GERAN and the A and/or Gb interfaces,is called A/Gb mode. GERAN refers to GSM/EDGE radio access network whichincludes GPRS and EDGE technologies.

The other leg of the system illustrates a mode of operation of themobile station (MS) 155 connected to the Core Network (CN) 105 via aUMTS terrestrial radio access network UTRAN. The air interface betweenthe UTRAN and the user equipment UE is called the Uu interface 160.

The UTRAN comprises one or more radio network subsystems (RNS) 165,(also called radio access networks) that are connected to the corenetwork CN 105 over an lu interface. Each RNS 165 is responsible for theresources of its cells. A radio network subsystem RNS 165 consists of aradio network controller (RNC) 170, and a multiplicity of nodes B 175,logically corresponding to base stations of traditional cellularsystems.

The radio network controller RNC is the network node responsible for thecontrol of the radio resources. The radio network controller RNC 170interfaces the core network CN and also terminates the RRC protocol(Radio Resource Control) that defines the messages and proceduresbetween the mobile and the UTRAN. It logically corresponds to a basestation controller in the GSM systems. On connections between the mobilestation 155 and the UTRAN, RNC 170 is the serving radio networkcontroller. As shown in FIG. 1, RNC 170 is connected to two CN nodes(MSC/VLR 135 and SGSN 140). In some network topologies it is alsopossible that one RNC is connected to one or more than two CN nodeswhich may be of similar or different type. For example, an RNC can beconnected to several SGSNs. This mode of operation of the MS, whenconnected to the Core Network via GERAN or UTRAN and the lu interface iscalled the lu mode.

It should be noted that only elements and units essential forunderstanding the invention are illustrated in FIG. 1. For a personskilled in the art it is clear that a communication system typicallycomprises a plurality of elements not shown in FIG. 1.

More precisely, the specification defines the Gb interface to existbetween a packet control unit (PCU) and a SGSN. The packet control unitis a functional unit responsible for various protocols in the GPRS MAC(Medium Access Control) and RLC (Radio Link Control) layers. Thesefunctions include establishment of RLC blocks for downlink transmission(towards the mobile station), de-assembly of blocks for uplinktransmission (towards the network), timing of PDCH (Packet DataChannel), channel access control functions (access request and accessgrants) and management functions of the radio channel, such as powercontrol, allocation and release of radio channels, broadcast of controlinformation, etc.

The packet control unit is connected to a channel codec unit (CCU) of abase station by means of an Abis interface. The functions of the channelcodec unit include channel coding functions (including co-directionalerror correction FEC and interleaving) and measuring functions relatedto the radio channel. The channel codec unit also establishes GPRS radioblocks, i.e. GPRS packets in which the data and signaling informationare sent over the radio interface Um. The channel codec unit is alwayslocated in a base station, but the PCU has a variety of alternativelocations, as shown in FIG. 2. When the packet control unit ispositioned remote from the base station, data is transmitted between thepacket control unit and channel codec units over the Abis interfaceusing PCU frames, which are extensions of the TRAU (Transcoder/rateAdaptor Unit) frames. Both GPRS data and GPRS MAC/RLC control signalsare transmitted in the PCU frames.

Option A of FIG. 2 illustrates a configuration where the packet controlunit PCU and the channel codec units are situated in a base station BTS.Option B illustrates a configuration where the packet control unit PCUis situated at the base station controller BSC site, for exampleimplemented as an adjunct unit to the BSC. Option C illustrates aconfiguration where the packet control unit PCU is positioned at theSGSN site. In configurations B and C the PCU is referred to as a remotePCU. The dotted line switch symbol refers to a packet-switchingfunction, and the solid line switch symbol refers to a circuit-switchingfunction, and the Um, Abis, and Gb interfaces are shown accordingly.

The air interface of the system in FIG. 1 allows signals from many usersto be multiplexed over the same physical resource. Resources are givento a user upon need and reallocated immediately thereafter. During itsoperation a packet control unit in a radio access network (RAN) node,which unit is arranged to control the use and integrity of the radioresources in a communication system, needs information regarding adefined group of other RAN cells. In the following, an embodiment of theinvention is described by using PCU operations and related communicationas an example. As explained above, in A/Gb mode the element controllingthe BTS cells is PCU and correspondingly in lu mode the elementcontrolling the node B cells is RNC. The scope of protection shouldtherefore not be interpreted merely through the A/Gb mode terminology ofthe specific embodiment. For example, depending on the mode ofoperation, the PCU could be replaced with an RNC element in thedescription.

The type of information to be exchanged between the radio access nodesvaries according to the functionality necessitating the informationexchange. Correspondingly, the criterion of defining the group of cellsregarding which the information is exchanged also varies for differentfunctionalities. As an example, a network controlled cell reselection(NCCR) procedure is discussed in more detail. A mobile station mayreceive neighboring cell system information on a packet associatedcontrol channel (PACCH). The neighboring cell system information iscontained in one or more instances of a PACKET NEIGHBOUR CELL DATAmessage. A mobile station, which receives this information stores thelast received set of the information for at least one cell. The receivedsystem information is valid for 30 seconds and can be used for initialaccess when entering a designated neighbor cell.

When a cell reselection is initiated by the network, the cell changeprocedure is started by sending a PACKET CELL CHANGE ORDER message tothe mobile station on the packet common control channel (PCCCH) orpacket associated control channel (PACCH). The PACKET CELL CHANGE ORDERmessage comprises characteristics of the new cell and a variety ofrelevant parameters. The PACKET CELL CHANGE ORDER message may alsocomprise the CONTAINER_ID referring to the one included in the receivedinstances of the PACKET NEIGHBOUR CELL DATA message. This is in order tomap the cell identity to the container identity for which neighbor cellinformation was received in the PACKET NEIGHBOUR CELL DATA messages. Inmanaging the procedure, the PCU needs to know the status of traffic loadin cells that are close to the current location of the mobile station.In terms of the present invention, the type of information in thisexample thus comprises cell load reports, and the criterion for choosingrelevant cells for the group of cells is that the cell should be aneighbor cell to the cell currently serving the mobile station.

As a further example of functionalities necessitating exchange ofinformation between RAN nodes, a base station system GPRS protocol(BSSGP) flush procedure can be mentioned. BSSGP is a protocol thatconveys routing information and quality of service related informationbetween a base station system (BSS) and a serving GPRS support node(SGSN). BSSGP supports the BSSGP virtual connections (BVC) so that eachcell always has one BVC over the Gb interface, and supports bothcell-specific (BVC) and MS-specific flow control. On receipt of adownlink logical link control (LLC) protocol data unit, a BSS willeither delete queued LLC protocol data units of a defined logical link,identified by a temporary logical link identity (TLLI), or move thequeued LLC protocol data units from an old to a new BVC. In a case wherethe mobile station has an existing BSS context and the BSS is not ableto move the queued LLC protocol data units, the BSS moves the BSScontext from the old to a new BVC, even if the new BVC is not able tooffer the same quality of service (QoS) parameters. The type ofinformation to be exchanged during flush operations comprises LLCprotocol data units and/or QoS parameters, and the group of relevantcells comprises at least one target cell at cell change.

For a person skilled in the art it is clear that the invented solutioncan be applied to various types of information and differently chosengroups of cells without deviating from the scope of protection.

In the following an embodiment based on NCCR is described in moredetail. According to the GSM/3G specifications, the BSS and a cellwithin the BSS are identified by adding a Cell Identity (CI) to thelocation area or routeing area identification. The CI is of fixed lengthwith 2 octets and it can be coded using a full hexadecimalrepresentation. The Cell Global Identification is the concatenation ofthe Location Area Identification and the Cell Identity. Cell Identity isunique within a location area. Neighboring relates herein to a criterionfor choosing the relevant cells for the load reporting functionality,and generally refers to a cell the area of which is limited to oroverlaps the area of the cell concerned.

FIG. 3 a illustrates configuration of a group of neighboring cells, andFIG. 3 b illustrates the logical configuration of base station systemsincluding these cells. In the embodiment of FIGS. 3 a and 3 b the unitsresponsible for controlling packets are shown according to option B ofFIG. 2, i.e. as located in BSC sites. BSC1 comprises two packet controlunits, PCU11 and PCU12. PCU11 controls cells cell1 and cell2, and PCU12controls cells cell3 and cell4. BSC2 also comprises two packet controlunits, PCU21 and PCU22. PCU21 controls cells cell5 and cell6, and PCU22controls cells cell7 and cell8. BSC3 also comprises two packet controlunits, PCU31 and PCU32. PCU31 controls cells cellA and cellB, and PCU32controls cells cellC and cellD. FIG. 3 b shows further a RNC comprisingtwo UTRAN packet control elements, here denoted as DMCU, that correspondto GERAN PCUs. RNC comprises two packet control units, RMCU11 andRMCU12. RMCU11 controls cells cellP and cellQ, and RMCU12 controls cellscellR and cellS.

In the beginning the mobile station is in cell 1 of BSC1, and as can beseen in FIG. 3 a, its neighboring cells are cell2 and cell3 of BSC1,cell 5 of BSC2, cellA of BSC3 and cellP. In order to be able to properlyimplement NCCR, PCU11 should know the load status in each of theseneighboring cells. A prior art PCU knows the neighboring cell IDs, butany other address information is not inherently stored in the packetcontrol units.

As discussed in the background of the invention, RIM procedures allowexchange of information between applications within RAN nodes. RIMallows the source BSS to send a message on the Gb interface to its SGSNincluding the source and destination addresses. All the messages usedfor the exchange of RIM information contain in their header theaddresses of the source and destination BSSs. Source and destinationaddresses have the same format. Each address contains a Mobile CountryCode (MCC), Mobile Network Code (MNC), Location Area Code (LAC),Routeing Area Code (RAC) and Cell Identity (CI).

Based on the Routeing Area Identity (MCC+MNC+LAC+RAC) of the destinationBSS address, the SGSN decides whether or not it is connected to thedestination BSS. If the SGSN is not connected to the destination BSS, itshall use the Routing Area Identification (RAI) to route the message tothe correct SGSN via the Gn interface. The SGSN connected to thedestination BSS decides which BSS to send it to on the basis of the CIof the destination address.

However, a packet control unit in a BSS controls its own cells and mayknow the cell IDs of the group of cells that fulfill the relevancecriterion, but it does not inherently know the address for packetswitched communication of the packet control unit that controls aspecific cell. This means that for PS communication, the addresses ofthe group of cells should be manually configured and maintained for eachcell in the packet control unit. For example in the embodiment of FIGS.3 a and 3 b, in order to allow packet switched delivery of load reportsfrom the neighboring cells cell2, cell3, cell5, cellA and cellP, the IPaddresses of the packet control units PCU12, PCU21, PCU31 and DMCU11should be manually configured to PCU11. Considering the amounts of cellsin practical implementations, it is clear that such amounts of manualoperations are not possible.

In the following the invented method is described by means of aGERAN-based system configuration. It should be noted that for clarity,only elements necessary for illustrating the invention are shown, andonly in one possible configuration. For a person skilled in the art itis clear that other configurations are possible, and that existing andfuture technologies facilitating the features claimed in the independentclaims fall within the scope of protection. FIG. 4 a shows a logicalconfiguration of two network cells and FIG. 4 b shows a flow chartillustrating the steps of the embodied method of the present invention,wherein the method facilitates management of cell-specific addressinformation for the operations of the first cell BTS1.

FIG. 4 a illustrates a configuration of two separate base stationsystems BSS1 and BSS2, and FIG. 4 b illustrates an embodiment of thepresent invention in the configuration of FIG. 4 a. The embodiment ofFIG. 4 a is illustrated with option B of FIG. 2, i.e. a packet controlunit PCU1 responsible for cell C1 is an adjunct unit of the base stationcontroller BSC1 of BSS1. Correspondingly, a packet control unit PCU2responsible for cell C2 is an adjunct unit of the base stationcontroller BSC2 of BSS2. Base station systems BSS1 and BSS2 areinterconnected via a core network CN. In FIG. 4 a, a configuration witha serving support node SGSN serving both base station controllers BSC1and BSC2 is shown as an example. In the invention the core networktransfers the relevant information transparently, and thus theconfiguration of the core network elements is not, as such, relevant forthe scope of protection. Transparency in this context pertains to afacility that allows a message to pass through the core network withoutthe core network interpreting the content of the message. A cell maycorrespond to a base station BTS or a node B. Alternatively a basestation or a node B site may comprise several cells that are identifiedwith different cell IDs.

RIM procedures provide an information transfer mechanism for exchanginginformation between applications within base station systems BSS1 andBSS2. In this embodiment the packet control units PCU1 and PCU2 compriseapplications APP1, APP2 that are arranged to exchange information usingthe RAN Information Management (RIM) procedures. The RAN information isspecified in section 8.1.5. of the 3GPP TS 23.060 V5.8.0 (2004-03)Technical Specification, 3rd Generation Partnership Project; TechnicalSpecification Group Services and System Aspects; General Packet RadioService (GPRS); Service description; Stage 2, (Release 5), which isincorporated herein by reference.

Consequently, the application in BSS1 first defines a group of cells(step 41), comprising one or more (up to N) radio cells of thecommunication system, that are, according to a defined selectioncriterion, relevant to a cell C1. The selection criterion may be, forexample that the cells cell_(i), i=1, . . . , N are neighbor cells ofC1. Starting from the first of the neighboring cells C2, the applicationgenerates a request that includes the cell identification of theneighbor cell C2 (step 42) and an information container that, accordingto the RIM procedure, shall not be interpreted by the Core Networknodes. The information container comprises a defined requestingapplication element to be interpreted by the application is thereceiving end. From the Routeing Area Identity of the destination BSS2address, the core network shall decide the destination base stationsubsystem BSS2. If the SGSN were not connected to the destination BSS2,it would use the RAI to route the message to the correct SGSN via the Gninterface. The SGSN connected to the destination BSS2 decides which BSS2to send the message to on the basis of the cell identification of thedestination address.

The application in BSS2 receives the requesting application element inthe information container and generates (step 43) a response includingan address information element that comprises the address for packetswitched information transfer in the communication system of FIG. 4 a.For example, the address may the IP address of the BSC2. The response istransferred from BSS2 to BSS1, again according to RIM procedures. APP1is further connected to a database DB1 in BSC1, and in response toreceiving the address information element updates the addressinformation to the database DB1 (step 44).

Hereafter the application checks (step 45) whether there exists anyother relevant cells. If yes, the procedure is repeated for each of therelevant cells. If not, the procedure will terminate.

FIG. 5 illustrates, as an example, a signaling sequence of a neighborcell PCU address query used to allow subsequent delivery of neighborcell PB load reporting requests without unnecessarily loading the SGSNelements that serve the BSS elements including the packet controlelements PCU1 and PCU2. It should be noted that the signaling messagesare shown to illustrate the logical elements exchanging the informationand the information content of the exchanged messages. The scope ofprotection is not limited to the terms and expressions used in thedescription. The first phase is the neighbor cell PCU address query(5.1) that is initiated with a RAN-INFORMATION REQUEST—message (5.11).The message carries the target cell ID (ID-D), the source cell ID (ID-S)and a PCU address query application container (AQ-C). SGSN receives thesignal and routes the RAN-INFORMATION REQUEST—message to BSS2 asdescribed above. PCU2 receives the message and generates aRAN-INFORMATION—message (5.13) comprising the IP address of PCU2 in thePCU address query application container, and forwards the message toSGSN, who routes the message (5.14) to PCU1. The IP address of PCU2 isstored in PCU1.

The second phase illustrates packet switched communication forexchanging load report information from the target cell (5.2). Theprocedure is initiated by a DIRECT-RAN-INFORMATION-REQUEST—message(5.21) from PCU1 to PCU2. The message includes IP addresses of PCU1 andPCU2, and a PCU PS load report application container carrying anapplication element to be interpreted by a corresponding application inthe receiving end. Reception of the application element in PCU2 triggersdelivery of load reports of the target cell from PCU2 to PCU1. The loadreports are carried in DIRECT-RAN-INFORMATION-messages, the messagesincluding the IP address of PCU2, the IP address of PCU1 and the PCU PSload report application container.

The advantage of the present invention is that it allows a mechanism toautomatically manage cell-specific address information in radio accessnetwork nodes. Furthermore, by means of the cell-specific addressinformation, data packets may be exchanged between packet control unitswithout incurring additional load to the Gb/lu interface, and/or to thecore network elements between the packet control units. This providesfor a variety of further advantageous applications, for example thepossibility to balance loads between neighboring cells independently,without dependencies on any of the circuit switched procedures of the Ainterface. The invented mechanism exploits existing informationmanagement procedures and can therefore be implemented without causingchanges to existing system specifications.

The application may be arranged to first request and store thecell-specific address information for each of the target cells, andthereafter update the information according to a defined plan. The planmay comprise, for example, periodic updates, wherein the addressinformation is requested and updated after defined time periods. Theplan may also comprise event-based updates, or a combination of these.

The invention also allows dynamic definition of groups for a cell. Forexample, configurations may change: new neighboring cells may beinstalled and/or some existing cells may be deleted. The application maybe further arranged to receive an indication on a change in thedefinition of the group of target cells and, in response to theindication, to update the cell-specific information automatically.

The selection criterion may be cell-specific or may be defined as a ruleapplicable to two or more cells. In order to avoid conflictingdefinitions, ubiquitous prevalence between possibly overlappingdefinitions is preferably defined.

The implementation of the described mechanisms in a packet control unitis illustrated with reference to FIG. 6. FIG. 6 provides a descriptionof a packet control unit that performs one or more of the previouslydescribed server functions. The packet control unit comprises processingmeans 61, an element that comprises an arithmetic logic unit, a numberof special registers and control circuits. Connected to the processingmeans are memory means 62, a data medium where computer-readable data orprograms or user data can be stored. The memory means typically comprisememory units that allow both reading and writing (RAM), and a memorywhose contents can only be read (ROM). The unit also comprises aninterface block 63 with input means 64 for inputting data for internalprocessing in the unit, and output means 65 for outputting data from theinternal processes of the unit. Examples of said input means comprise aplug-in unit acting as a gateway for information delivered to itsexternal connection points. Examples of said output means include aplug-in unit feeding information to the lines connected to its externalconnection points. The processing means 61, memory means 62, andinterface block 63 are electrically interconnected for performingsystematic execution of operations on the received and/or stored dataaccording to the predefined, essentially programmed processes of theunit. In a solution according to the invention, the operations comprisea functionality for implementing the operations of the packet controlunit described above.

It will be obvious to a person skilled in the art that, as technologyadvances, the inventive concept can be implemented in various ways. Theinvention and its embodiments are not limited to the examples describedabove but may vary within the scope of the claims.

1. A functional unit of a radio access network said functional unitcomprising: first receiving means for receiving a request for a packetswitched communication address of a second radio access network nodecomprising the functional unit, wherein the functional unit is includedin a communication system comprising the radio access network and a corenetwork; generating means for generating, in response to receiving therequest, a response comprising the packet switched communication addressof the second radio access network node; second receiving means forreceiving the request from a first radio access network node; andtransmitting means for transmitting the response to the first radioaccess network node in information containers transparently to the corenetwork.
 2. A radio access network node comprising: a functional unit;first receiving means for receiving a request for a packet switchedcommunication address of a second radio access network node comprisingthe functional unit; generating means for generating, in response toreceiving the request, a response comprising the packet switchedcommunication address of the second radio access network node; secondreceiving means for receiving the request from a first radio accessnetwork node; and transmitting means for transmitting the response tothe first radio access network node in information containers that aretransparent to a core network.
 3. A computer program product, executableon a computer, wherein execution of the computer program product in auser equipment causes a packet control unit to: receive a request for apacket switched communication address of a second radio access networknode comprising a functional unit; generate, in response to receivingthe request, a response comprising the packet switched communicationaddress of the second radio access network node; receive the requestfrom a first radio access network node; and transmit the response to thefirst radio access network node in information containers that aretransparent to a core network.
 4. A functional unit of a radio accessnetwork, said functional unit comprising: a first receiving unitconfigured to receive a request for a packet switched communicationaddress of a second radio access network node comprising the functionalunit, wherein the functional unit is included in a communication systemcomprising the radio access network and a core network; a generatingunit configured to generate, in response to receiving the request, aresponse comprising the packet switched communication address of thesecond radio access network node; a second receiving unit configured toreceive the request from a first radio access network node; and atransmitting unit configured to transmit the response to the first radioaccess network node in information containers transparently to the corenetwork.
 5. A radio access network node comprising: a functional unit; afirst receiving unit configured to receive a request for a packetswitched communication address of a second radio access network nodecomprising the functional unit; a generating unit configured togenerate, in response to receiving the request, a response comprisingthe packet switched communication address of the second radio accessnetwork node; a second receiving unit configured to receive the requestfrom a first radio access network node; and a transmitting unitconfigured to transmit the response to the first radio access networknode in information containers that are transparent to a core network.